Making metal-sheathed cables



Aug. 5, 1941. L, E, FOGG 2,251,826

MAKING METAL-SHEATHED CABLES Filed Dec. 18, 1959 3 Sheets-Sheet l Aug.5, 1941. L. E. FOGG MAKING METAL-SHEATHED CABLES 3 Sheets-Sheet 2 FiledDec. 18, 1959 Aug. 5, 1941. L, E, FOGG 2,251,826

MAKING METAL-SHEATHED CABLES Filed Dec. 18, 1939 3 Sheets-Sheet 3Patented Aug. 5, 1941 AUNITED STATES PATENT OFFICE MAKING METAL-SHEATHEDCABLES Leigh E. Fogg. East Providence, R. I., assignor to Kennecott Wireand Cable Company, Phillipsdale, R. I., a corporation ApplicationDecember 18, 1939, Serial No. 309,736

3 Claims.

This invention relates to improvements in processes of makingmetal-sheathed cables, and more particularly to processes of makingmetalsheathed paper or the like insulated electrical cables.

One object of this invention is to provide an improved process of makinga metal-sheathed cable whereby the cable-core 'can be more elllcientlytreated to remove moisture and prevent the reabsorption of the same bythe cable-core.

Another object of this invention is to provide an improved process ofmaking a metal-sheathed cable by enclosing a cable-core inloosely-fitting relation with a cable-sheath and extracting theymoisture and the gas from the cable-core and saturating the latter withinsulating material, and reducing the diameter of the cable-sheath tobring it into close fitting engagenent with the cable-core. (if

With the above and other objects in view, as will appear to tiioseskilled in the artfrom the present disclosure, this invention includesall features in the 'said disclosure which are novel over the prior at.

In the accompanying drawings forming part of the present disclosure, inwhich certain ways of carrying out the invention are shown forillustrative purposes:

Fig. 1 is a side elevation of one form of apparatus for performing thefirst-stage reduction of the cable-sheath;

Fig. 2 is a transverse sectional view on line 2--2 of Fig. 1;

Fig. 3 is a transverse sectional view on line 3-3 of Fig. 1;

Fig. 4 is a longitudinal sectional view on line 4 4 of Fig. 1;

Fig. 5 is a schematic side elevation of one form of apparatus forperforming the second-stage or final reduction of the cable-sheath;

Fig. 6 is a .transverse sectional View on line 6 6 of Fig. 1;

Fig. '7 is a transverse sectional view on line 1-1 o1' Fig. 1;

Fig. 8 isa transverse sectional view Online 8-8 of Fig. 5; and ji Fig. 9is a view similar to Fig. 5 of another form of apparatus for performingthe secondstage or final reduction of the cable-sheath.

In the description and claims, the various parts and steps areidentified by specific names for convenience, but .they are intended tobe as generic in their application as the prior art will permit.

Fig. 6 shows cable I 0 including a cable-core Il loosely assembled in ametal cable-sheath I2,

and with the space between the 'core and sheath illledwith insulatingoil orlmaterial or compound i3 which also impregnates the paper or thelike insulation covering, forming part of the cable-core. A suitableloose-fitting relation between the core and sheath,'depen'ding on .thediameter and length of the cable, is obtained by having the externaldiameter of the core from about 115 to about 1A." smaller than theinternal diameter of the sheath. Prior to 'introducing the insulatingmaterial I3 into the space between the core and sheath in theconstruction illustrated in Fig. 6, the core within` the looselyfittingsheath is suitably treated to remove moisture and gas, after 'which theinsulating material or compound i3 is introduced into the space betweenthe core andsheath, and the sheath is later reduced inl diameterv sothat the core and sheath are in close relationship.

But inasmuch as the insulating material which it is desirable to use isof relatively-high viscosity at ordinary room temperatures, I havefoundthat instead of attempting to completely reduce the cable-sheathfrom the diameter shown in Fig. 6 tothat shown in Fig. 8 in a singleoperation, that marked advantages result from dividing this reducingoperation into at least two stages, in the first of which stages thesheath is reduced to near its final size. as illustrated in Fig. 7, andsubsequently the sheath is reduced the final small amount to bring itinto final close-fitting relation with the core, as

`illustrated in Fig. 8. During the iirst or major reduction of thesheath, I have found that it is highly desirable to have theinsulatingcompound (and the sheath and core) at an elevated temperature such, forexample, as at from to C., while the second or final stage of thereduction is carried out with the sheath and its 'contents at a normalroom temperature of about 25 C. For typical widely-used insulatingcompounds, the viscosity at 25 C. is from 1600 to 3700 centipoises,whereas at 100 C. it is from 17 to 27 centipoises.

Thus, by making the rst-stage reduction of the sheath while theinsulating material is heated and consequently of relatively-lowviscosity, permits it to flow longitudinally of the cable between thecore and sheath as the reduction in size of the sheath takes place. Onthe other hand, if the insulating material were not in a heatedcondition, its viscosity would be so high that the closing in orreducing operation on the sheath would produce so high a pressure in theinsulatingcompound along the portion oi the sheath adjacent to the placeof reduction in diameter. that dangerous bursting stresses would bedeveloped which would tend to :burst or unduly bulge the sheath. Afterthe rst-stage reduction operation has been completed at an elevatedtemperature, the entire cable, including the insulating compound, ispermitted to cool to ordinary temperatures. This, however, causes agreater shrinkage of the insulating compound than of the other parts ofthe cable, with the consequence that voids or spaces occur between thecore and sheath along the length of the cable. To eliminate these voidspaces in the insulating compound, the second-stage or iinal reductionoi' the sheath is brought about. But inasmuch as this ilnal-stagereduction is made while the insulating compound is at ordinary roomtemperature and, therefore, at relativelyhigh viscosity, in order toavoid bringing about undue bulging or bursting pressures in theinsulating compound within the cable, considerable care is needed not toapply too great reduction in diameter of the cable-sheath. Control ofthis operation can be accomplished by automatic means, as will be latermore fully set forth.

Figs. 1 to 4 show views of an apparatus for bringing about thefirst-stage or main reduction oi the sheath of the cable. Rotatablymounted on the frame or base I4 is a lower roll I5 having side-ilangesI6 between which fits an upper roll Il having a semicylindrlcal grooveI8 which with the straight side-faces I8 form relatively-sharp outeredges 20, and with the semicylindrical groove 2i of the lower roll i5forms a cylindrical area (Fig. 3). The upper roll Il is rotatablymounted on a slide 22 which can be adjustably pressed downward by ascrew 23 carrying a handwheel 24. A second pair of grooved rolls 25 and26 are arranged at right angles to the ilrst pair of rolls I5, Il, theroll 25 being rotatably mounted on the frame or base i4, and the roll 25being rotatably mounted on a slide 2l which can be Y adjustably forcedtoward the roll 26 by means of a screw 28 carrying a hand-wheel 29.

Fig. 2 illustrates the manner in which the sheath is distorted from theround form shown in Fig. 6 to elliptical form as it starts in betweenthe rolls i and il, while Fig. 3 illustrates the completion of thefirst-stage reduction operation after it has passed through the pair ofrolls I5 and I'l. The second pair of rolls 25 and 26 mainly removes anyiins that may be formed by the edges as a result of passage through thepair of rolls I5 and I 1. The cable is then permitted to cool down -toordinary temperature with the result that the insulating compound I3 inthe cable shrinks more than the cable-sheath, thereby causing voids orspaces to occur between the core and sheath along the length of thecable. In order to eliminate these voids or spaces, the cable is thenpassed through suitable mechanism such, for example, as that illustratedin Fig. 5, in order to further reduce the diameter of the sheath andeliminate the voids or spaces. But inasmuch as the insulating compoundin the sheath has now become very viscous, great care is necessary infurther reducing the cable so as not to cause too great a longitudinalilow of the insulating compound with consequentexcess of bulging orbursting stresses being imposed upon the sheath. In order to accomplishthis result, it is desirable to ilnally reduce the cable-sheath by meansoi an apparatus in which the reduction of the sheath is controlled moreor less automatically to avoid undue bursting stresses on the sheath.

Referring to the apparatus illustrated in Fig. 5, the cooled-oir cable,illustrated in Fig. '7 in cross section, is drawn between the pair ofrolls Il and li and wound onto a drum l! by means of an electric motorI3. A guide-roll 34 is used to position the cable in -asubstantially-horizontal position as it enters Ithe rolls II-IL The roll34 is rotatably mounted in ilxed poistion on a base na, while the rollIl is rotatably mounted on a slide 35 vertically slidable in a frame lland having secured to the slide, a screw-threaded rod Il threadedlyengaged by a worm-wheel Il driven by a worm l! driven from a reversibleelectric motor 4I through a friction-clutch 4| and a reducing-gear unit42.

A follower-rod 43 carries a roller 44 at its lower end which is pressedinto contact with the cable I0 by a spring 45 and is pivoted at itsupper end to a switch-lever or arm 4I which latter is pivoted to theframe 36. The switchlever 46 has secured at one end thereof, an electriccontact 41 adapted to engage contacts 48, 49, 5l and 5i under certainconditions. The contacts 4l to 5i are merely schematically illustrated,and in actual fact may consist of any suitable type of switches such,for example, as mercury switches which are actuated by tilting.

Assume now that the rolls 30, 3| in Fig. 5 are adjusted to close-in thecable from the condition shown in Fig. 7 to its ilnal closed-in stageshown in Fig. 8, and assume the main switch 52 to be closed, asillustrated. This will supply electric power to the reeling-motor 33,which thus draws the cable III to the left in the direction of the arrow53. Prior to formation of a bulge 54 in the cable-sheath. theswitch-lever 46 will close electric contacts to cause the roll 3| totravel down closer to roll 30, as will be later more fully described,or, the switch-lever 46 could be temporarily held in neutral oropencircuit position, but in either case, presently the insulating oilor compound within the cable starts to be crowded to the right withinthe sheath of the cable with suillcient force to expand the cablesufilciently to produce a slight bulge 54 which is sufficiently large toraise the roller 44 and follower-rod 43 to cause the switch-lever 46 tooccupy the midway or open-circuit position, so that all electricalcontacts operated by it are in open condition. Now assume that anadditional accumulation of insulating compound enlarges the bulge 54still more and thus pushes the follower-rod 43 up against the action ofthe spring 45 and swings the switch-end of the switch-lever 46 downwardto close the contacts 41 and 4I, with the result that the magneticswitch-closer or contactor 5l closes the doublepole switch 5l againstthe action of the spring 51, to thus start the motor 4I at slow speed toactuate the mechanism to raise the roll Il to relieve the pressuresomewhat upon the cable I I. If this results in sumcient release,sumcient excess insulating compound will be permitted to move forwardwith the cable to cause the bulge 54 on the cable to become smaller insize as the cable is wound on the drum l2, with the result that theroller 44 descends, thus permitting the spring 45 to swing theswitch-lever 45 and break the circuit formed by the switch-contacts 41and 4I, thus stopping the motor 4l. Preferably, the roll 3| will bemoved very slowly so that perhaps ten feet or more of cable will movebetween the rolls 30, 3| while an adjustment of rc-li 3! of only a fewthousandths of an inch is made.

But if instead of the foregoing described raising of the roll 3| beingsuilicient to relieve the stress, it should happen that the accumulationof insulating oil or material in the cable causes even a larger bulgenotwithstanding the action of the motor 40 to relieve this condition byraising the roll 3|, then the switch-arm 46 is swung still further, toclose the contacts 41 and 49, while maintaining the contacts 41 and 46closed, thereby acting on the magnetic switch-closer or contactor 56 toclose the single-pole switch 69 against the action of the spring 66 andthus short circuit the resistance coil. 6|, with the result that themotor 40 increases in speed and, therefore, works faster to raise theroll 3| faster to overcome the tendency to increase the size of thebulge 54 in the cable-sheath. If this action has now been successful incausing the bulge on the cable-sheath to become smaller, then the roller44 is forced downward by the spring 45 to thus swing the switch-arm 46to successively break the two sets of switch-contacts 41, 49 and 41, 46with the result that the circuit to the motor 46 is broken and it cornesto a stop.

If, however, there is insuflicient bulge produced in the cable-sheath,then roller 44 descends so far as tocause the switch-arm 46 to swing andengage the switch-contacts 41 and 50 with the result that the magneticswitch-closer or contactor 62 actuates the double-pole switch 63 againstthe action of the spring 64 to closed position, thus supplying power tothe armature of the motor 40 in the opposite direction and thus causingthe motor 40 to rotate in the reverse direction, with the result thatthe upper roll 3| is forced downwardly toward the roll 30. If the bulge54 continues to decrease in size, then the switch-arm 46 will swingfurther to close the switch-contacts 41 and 5|, while maintaining thecontacts 41, 50 closed, to thus actuate the switch-closer 56 to closethe single-pole switch 59 against the action of spring 60 to thus shortcircuit the resistance coil 6| and, in consequence, speed up the actionof the motor 40 to thus force the roll 3| downward even faster. Whennally a proper slight degree of bulge occurs in the cable-sheath, thenthe switch-contacts 41, and 41, 56 again open, and the switch-arm 46remains in open-circuit position ready to act in either direction toaccomplish the adjustment of the roll 3| in one direction or the otheras heretofore described.

In the form of the invention illustrated in Fig. 9 which is amodification of the form of the invention illustrated in Fig. 5, such ofthe parts as bear the same reference characters in Fig. 9 as they do inFig. 5, are essentially the same as the corresponding parts in Fig. 5.Referring to Fig. 9 when the follower or feeler roll 44 is raised bypressure from the bulge 54 of the cable I6 to cause the follower rod 43to swing the switch-lever or arm 65 upward to close the electriccontacts 66 and 61, the switch-closer 55 closes the double-switch 56against the action of the spring 51 to cause the reversible electricmotor 66 to start in operation at the same time that the brake-releasecoil 69 releases the spring-held brake 10, which normally holds theshaft of the motor 66 stopped, thus, through the train of drive elements4|, 42, 39 and 38, raising the screwthreaded rod 31 and the slide 35upward, which slide carries along with it the electric-contacts 61 and1| which are mounted on an insulation support 12 mounted on the slide,thus breaking the circuit between the contacts 66 and 61 with the resultthat the double-pole switch 66 is opened by the spring 51 thus breakingthe circuit to the motor 66 and the brake-release coil 66 in consequenceof which the motor 66 stops and the brake 10 is applied, thus quicklystoppingvthe shaft of the motor. If the bulge 54 continues to enlargeand thus again brings the contact 66 in engagement with contact 61, thepreceding series of operations is repeated and the motor 66 is againbrought to a stop as previously described.

If now the bulge 54 sufficiently decreases in size to cause theswitch-lever 65 to swing downwardly and engage the contacts 1| and 13,then the switch-closer 62 closes the double-pole switch 63 against theaction of the spring 64 and thus actuates the motor 66 in the reversedirection at the same time that the brake-release coil 66 is actuated,to thus cause the screw-rod 31 and the slide 35 to move downward untilthe circuit is broken between the contacts 1| and 13, whereupon themotor is stopped as previously described. But if the bulge 54 continuesto grow smaller, then the contacts 1| and 13 are again engaged and themotor is started up again until the contacts 1|V and 13 are againseparated to thus again cause the motor 68 to stop. If desired, ornecessary, adjustable limit means such as a screw 14 might be mounted,as for example on the frame 36, to prevent the roll 3| from moving downtoo close to the roll 30.

In the form of the invention illustrated in Fig. 9, as will be seen fromthe description Just given, while an above-normal size of bulge exists,the motor 66 will continue to operate to separate the rolls 30, 3| onlywhile the bulge continues to enlarge. And similarly, while anunder-normal size bulge exists, the motor will continue to operate toclose the rolls closer together only while the bulge continues to becomesmaller.

The invention may be carried out in other spe cifc ways than thoseherein set forth without departing from the spirit and essentialcharacteristics of the invention,and the present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

I claim: v

l. The process of making a metal-sheathed cable comprising: assembling acable-core having solid insulation thereon in a loosely-fitting metalcable-sheath, the maximum diameter of said cable-core being considerablyless than the corresponding internal diameter of said cablesheath;extracting moisture from the cable-core while it is in loosely-fittingrelation with the cable-sheath; filling the remaining space in saidcable-sheath with iiowable insulating compound which is of relativelyhigh viscosity at ordinary temperatures and of relatively low viscositywhen suitably heated; reducing the diameter of said cable-sheath tonearly final size while said insulating compound is heated to atemperature at which it is of relatively-low viscosity, the internalshape of such reduced sheath being substantially the same as the shapeoi' said cablecore; and further reducing the diameter of thecable-sheath to final size after said insulating compound has cooled toa condition of relatively high viscosity.

2. 'I'he process of making a. metal-sheathed cable comprising:assembling a cable-core in a loosely-fitting metal cable-sheath;filling. the remaining space in said cable-sheath with iiowableinsulating material which is of relativelyhigh viscosity at ordinarytemperatures and of relatively-low viscosity when suitably heated;reducing the diameter ot said cable-sheath to nearly final size whilesaid insulating material is heated to a temperature at which it is ofrelatively-low viscosity; and further reducing the diameter oi' thecable-sheath to iinal size after said insulating material has cooled toa condition of relatively-high viscosity by reducing means which isadjusted to vary the final diameters of dliferent sections of thecablesheath in accordance with the tendency of said insulating materialto enlarge the cable-sheath during the final reducing operation.

3. 'I'he process of making a metal-sheathed cable comprising: assemblinga cable-core in a 20 loosely-fitting metal cable-sheath; nlling theremaining space in said cable-sheath with ilowable insulating materialwhich is of relativelyhigh viscosity at ordinary temperatures and otrelatively-low viscosity when suitably heated: reducing the diameter o!said cable-sheath to nearly final size while said insulating material isheated to a temperature at which it is of reiatively-low viscosity; andfurther reducing the diameter oi the cable-sheath to iinal size aftersaid insulating material has cooled to a condition of relatively-highviscosity by a pair of reducing rolls which are automatically adjustedrelatively to one another to vary the iinal diameters of differentsections of the cable-sheath in accordance with the tendency of saidinsulating material to enlarge the cable-sheath during the inal reducingoperation.

LEIGH E. FOGG.

